Crawford Katie E, Hedtke Shannon M, Doyle Stephen R, Kuesel Annette C, Armoo Samuel, Osei-Atweneboana Mike Y, Grant Warwick N
Department of Animal, Plant and Soil Sciences, La Trobe University, Bundoora, Victoria, Australia.
Department of Animal, Plant and Soil Sciences, La Trobe University, Bundoora, Victoria, Australia; Department of Environment and Genetics, La Trobe University, Bundoora, Victoria, Australia.
Int J Parasitol. 2024 Mar;54(3-4):171-183. doi: 10.1016/j.ijpara.2023.11.002. Epub 2023 Nov 20.
National programs in Africa have expanded their objectives from control of onchocerciasis (river blindness) as a public health problem to elimination of parasite transmission, motivated by the reduction of Onchocerca volvulus infection prevalence in many African meso- and hyperendemic areas due to mass drug administration of ivermectin (MDAi). Given the large, contiguous hypo-, meso-, and hyperendemic areas, sustainable elimination of onchocerciasis in sub-Saharan Africa requires delineation of geographic boundaries for parasite transmission zones, so that programs can consider the risk of parasite re-introduction through vector or human migration from areas with ongoing transmission when making decisions to stop MDAi. We propose that transmission zone boundaries can be delineated by characterising the parasite genetic population structure within and between potential zones. We analysed whole mitochondrial genome sequences of 189 O. volvulus adults to determine the pattern of genetic similarity across three West African countries: Ghana, Mali, and Côte d'Ivoire. Population genetic structure indicates that parasites from villages near the Pru, Daka, and Black Volta rivers in central Ghana belong to one parasite population, indicating that the assumption that river basins constitute individual transmission zones is not supported by the data. Parasites from Mali and Côte d'Ivoire are genetically distinct from those from Ghana. This research provides the basis for developing tools for elimination programs to delineate transmission zones, to estimate the risk of parasite re-introduction via vector or human movement when intervention is stopped in one area while transmission is ongoing in others, to identify the origin of infections detected post-treatment cessation, and to investigate whether persisting prevalence despite ongoing interventions in one area is due to parasites imported from others.
非洲的国家项目已将其目标从将盘尾丝虫病（河盲症）作为一个公共卫生问题进行控制，扩大到消除寄生虫传播。这一转变的动力来自于在许多非洲中度和高度流行地区，由于大规模使用伊维菌素进行药物驱虫（MDAi），盘尾丝虫感染率有所下降。鉴于撒哈拉以南非洲存在大片连续的低度、中度和高度流行区域，要在该地区可持续地消除盘尾丝虫病，就需要划定寄生虫传播区的地理边界，以便项目在决定停止MDAi时，能够考虑到通过媒介或人类迁移，从仍有传播的地区重新引入寄生虫的风险。我们建议，可以通过描绘潜在区域内和区域间的寄生虫遗传种群结构来划定传播区边界。我们分析了189条盘尾丝虫成虫的完整线粒体基因组序列，以确定三个西非国家（加纳、马里和科特迪瓦）的遗传相似模式。种群遗传结构表明，加纳中部普鲁河、达卡河和黑沃尔特河附近村庄的寄生虫属于一个寄生虫种群，这表明数据并不支持流域构成独立传播区的假设。来自马里和科特迪瓦的寄生虫在基因上与来自加纳的寄生虫不同。这项研究为制定消除项目工具提供了基础，这些工具可用于划定传播区、估计在一个地区停止干预而其他地区仍在传播时，通过媒介或人类移动重新引入寄生虫的风险、确定治疗停止后检测到的感染源，以及调查在一个地区尽管持续进行干预但患病率仍居高不下是否是由于从其他地区输入的寄生虫所致。
